Tian-Calvet Microcalorimeter Research Articles

Reaction enthalpies for the hydrogenation of alkyl levulinates and levulinic acid on Ru/C– influence of experimental conditions and alkyl chain length

The development of process flow diagrams requires knowledge of reaction enthalpy for pinch analysis and thermal risk assessment. Such information is missing for some biomass processes, such as the production of γ-valerolactone (GVL) from the hydrogenation of levulinic acid or alkyl levulinate. To fill this gap, this manuscript describes a detailed calorimetric study on the hydrogenation of levulinic acid (LA), methyl levulinate (ML), ethyl levulinate (EL), propyl levulinate (PrL), butyl levulinate (BL) and pentyl levulinate (PeL) over Ru/C. This reaction system occurs through a two-step pathway with a domino hydrogenation/cyclization sequence. The cyclization step (lactonization) was found to be endothermic and was evaluated by a Tian-Calvet C80 micro-calorimeter, whereas the hydrogenation step was found to be exothermic and was tracked by a RC1 Mettler Toledo High-Pressure calorimeter. It was verified that reaction enthalpy is independent of reaction temperature (in the operating conditions used in this work), levulinate concentration and solvent (levulinate, corresponding alcohol or GVL). It was also found that reaction enthalpy for both steps did not depend linearly on alkyl chain length.

Calorimetric study of methanol adsorption in LiZSM-5 and CsZSM-5 zeolites

This paper presents isotherms and basic (ΔH, ΔF, and ΔS) thermodynamic characteristics of methanol adsorption in Li3,37ZSM-5 and Cs3,17ZSM-5 zeolites obtained by the calorimetric method. For measurements of isotherms and differential heat of adsorption, a system consisting of a universal high-vacuum adsorption unit and an attached differential modified Tian-Calvet type microcalorimeter, DAC-1-1A, which directly quantifies and qualifies the nature and forces of adsorption interaction, was used. The adsorption isotherm is described by the equations of the volumetric micropore filling theory (VMOT). The correlation between the adsorption-energy characteristics is found, and the molecular mechanism of methanol adsorption in Li3,37ZSM-5 and Cs3,17ZSM-5 zeolites throughout the filling region is revealed. Methanol adsorbed in Li3,37ZSM-5 and Cs3,17ZSM-5 zeolites is located in the first coordination sphere with cations Li+ and Cs+, forming tetra- and trimeric complexes. It is found that the charge density significantly affects the adsorption mechanism, the adsorption energy, and the number of adsorbed molecules. It was determined that the average molar entropy of ammonia adsorption on LiZSM-5 and CsZSM-5 zeolites indicates that the mobility of methanol molecules in the zeolite is below the liquid phase and close to the mobility of the solid phase, indicating a strong inhibition of mobility of methanol adsorbed on cations. This work shows how calorimetric data can complement crystal structure results and detect subtle adsorbent/adsorbate interactions at the molecular level.

An initial evaluation of the thermodynamic or kinetic separation performance of cation-exchanged LTA zeolites for mixtures of propane and propylene

Adsorptive separation of propylene (C3H6) and propane (C3H8) may represent an energy-efficient alternative to conventional cryogenic distillation. In this perspective, a set of zeolitic adsorbents of LTA type structure (pure-silica zeolite (Si-LTA) and cation- (Na+, 33% of Li+, 50% of Mg2+ and 50% of Ca2+) containing zeolites) were prepared, then characterized using various techniques such as PXRD, gas adsorption measurement, TGA, XRF, SEM and EDX mapping. Thanks to an in-house manometric dosing setup coupled with a Tian-Calvet type microcalorimeter, the pure gas adsorption isotherms and their corresponding differential enthalpies of adsorption were measured at 303 K and for pressures up to 5 bar. To fit those adsorption data, the dual-site Langmuir was selected as the best fit model, and by using the Ideal Adsorbed Solution Theory (IAST), thermodynamic selectivities were determined. The mass transfer constants were also estimated by fitting, separately, the Linear Driving Force (LDF) and isothermal micropore diffusion models to adsorption kinetic curves, thus allowing kinetic type selectivities to be calculated. The combination of those selectivities reveals that the thermodynamic separation of C3H6 from C3H8 is highly favorable on CaNa-LTA, followed by its MgNa-LTA counterpart with IAST selectivities around 15 and 5, respectively. On the other hand, the monovalent cationic zeolites (i.e., Na- and LiNa-LTA) show a predominance of steric effects. Also, except for Si-LTA which shows a moderate kinetic separation, the studied materials are potential candidates, in the following order CaNa- > MgNa- > LiNa- > Na-LTA, for the separation of C3H6 from C3H8 by adsorption-based technologies.

Thermodynamics of mixtures containing amines. XVII. [formula omitted] and [formula omitted] measurements for benzylamine + heptane or + 1-alkanol mixtures at 298.15 K. Application of the DISQUAC and ERAS models

Excess molar enthalpies, HmE, at 298.15 K and 0.1 MPa have been measured by means of a Tian-Calvet microcalorimeter for the systems benzylamine (phenylmethanamine) + heptane, or + methanol, or + 1-propanol, or + 1-pentanol, or + 1-heptanol, or + 1-decanol. In addition, excess molar volumes, VmE, at the same conditions have been also determined using a densimeter Anton Paar model DSA 5000 for the benzylamine + heptane mixture. The HmE of this solution is large and positive since at 298.15 K the system temperature is close to its upper critical solution temperature. Thus, systems with n-alkanes show positive deviations from the Raoult's law. The measured |VmE| values are low, indicating the existence of large structural effects. HmE values of mixtures involving 1-alkanols are large and negative. That is, interactions between unlike molecules are dominant and the systems are characterized by negative deviations from Raoult's law. It is shown that the enthalpy of the hydrogen bonding between molecules of 1-alkanol and benzyalmine are more negative than those between 1-alkanol molecules. The VmE values of the systems with 1-alkanols are also large and negative, and are determined mainly by interactional effects since they increase in line with HmE and with the alcohol size. The different contributions to HmE have been evaluated. The systems have been studied using the DISQUAC and ERAS models. ERAS describes correctly the VmE function. DISQUAC largely improves ERAS results on HmE or on excess molar heat capacities at constant pressure for the mixtures with 1-alkanols, which underlines that physical interactions are very relevant in such solutions.

Physicochemical and Calorimetric Study of Aluminocopiapite and Thermodynamic Properties of Copiapite-Group Minerals

The natural basic aqueous aluminum and iron sulfate, aluminocopiapite (Al0.60 $${\text{Fe}}_{{0.07}}^{{3 + }}$$ ) $${\text{Fe}}_{{4.00}}^{{3 + }}$$ [SO4]6.03(OH)1.95 ⋅ 19.54H2O (Blyava, South Urals, Russia), was studied using powder X‑ray diffraction, infrared and Mossbauer spectroscopy, and thermal analysis. The enthalpy of formation from the elements $${{\Delta }_{f}}H_{{el}}^{0}$$ (298.15 K) = −11 826 ± 58 kJ/mol was determined by high-temperature melt solution calorimetry on a Tian-Calvet high-temperature heat-flux microcalorimeter “Setaram” (France). Standard entropies and Gibbs energies of formation were estimated for the studied aluminocopiapite and other copiapite-group minerals.

Thermodynamics of mixtures with strong negative deviations from Raoult’s law. XVIII: Excess molar enthalpies for the (1-alkanol + cyclohexylamine) systems at 298.15 K and modelling

Excess molar enthalpies, HmE, have been measured using a Tian-Calvet microcalorimeter for the systems CH3(CH2)u-1OH (u = 1,2,3,4,7,10) + cyclohexylamine at 298.15 K and 0.1 MPa. The HmE values are large and negative, indicating the existence of strong interactions between unlike molecules, which is consistent with the also large and negative excess molar volumes, VmE of these solutions, previously measured by us. The contribution from the equation of state term to HmE has been evaluated for the 1-alkanol + cyclohexylamine, or + 1-hexylamine, or + aniline mixtures, and the corresponding excess molar internal energies at constant volumes, Um,VE, determined. It is shown that such contribution is particularly important for the methanol + aniline system, in such way that the excess functions HmE and Um,VE have different sign at x1 = 0.5. The DISQUAC and ERAS models have been applied to the cyclohexylamine systems, and the interaction parameters reported. DISQUAC improves ERAS results on HmE. The latter model describes correctly the VmE curves. The variation of HmE of CH3(CH2)u-1OH + cyclohexylamine, or + 1-hexylamine, or + aniline mixtures with u along a homologous series with a given amine, or with the amine in mixtures with a given 1-alkanol is discussed in terms of the different interactional contributions to HmE.

Thermal and Thermochemical Study of Blödite (Astrakhanite)

The natural hydrous sodium−magnesium sulfate blodite (astrakhanite) Na2Mg(SO4)2 · 4H2O from sediments of saline Lake Bai Shagyr (Russia) is studied. The stages of its decomposition on heating are distinguished using thermal analysis, X-ray diffraction, IR and Raman spectroscopy. The enthalpy of formation of blodite from elements ( $${{\Delta }_{f}}H_{{el}}^{0}$$ (298.15 K) = –3845 ± 13 kJ/mol) is determined on a Tian-Calvet microcalorimeter using high-temperature melt solution calorimetry. The values of standard entropy and Gibbs energy of mineral formation are estimated.

Natural Magnesium Hydrous Orthophosphates Bobierrite and Kovdorskite: FTIR, Raman, Thermal, and Thermochemical Study

A physicochemical study of natural hydrous magnesium orthophosphates bobierrite Mg3[PO4]2 · 8H2O and kovdorskite Mg2[PO4](OH) · 3H2O from the Kovdor carbonatite massif, Kola Peninsula, Russia, was carried out using X-ray diffraction, infrared spectroscopy, Raman spectroscopy, and thermal analysis. The enthalpies of dehydration of the minerals were measured using a NETZSCH DSC 204 F1 differential scanning calorimeter, the enthalpies of formation from the elements for bobierrite (–6167 ± 16 kJ/mol) and kovdorskite (–3251 ± 10 kJ/mol) were determined by high-temperature melt solution calorimetry on a Setaram high-temperature heat-flux Tian–Calvet microcalorimeter. The values of their standard entropies and Gibbs energies of formation are estimated.

Thermodynamic properties of montechellite

A thermochemical study of natural calcium and magnesium orthosilicate ─ monticellite (Ca1.00Mg0.95)[SiO4] (Khabarovsk Territory, Russia) was carried out on the Tian-Calvet microcalorimeter. The enthalpy of formation from the elements fHоel(298.15 K) = -2238.4 4.5 kJ / mol was determined by the method of high-temperature melt solution calorimetry. The enthalpy and Gibbs energy of formation of monticellite of the theoretical composition of CaMg[SiO4] are calculated: fH0el(298.15 K) = -2248.4 4.5 kJ/mol and fG0el(298.15 K) = -2130.5 4.5 kJ/mol.

Thermodynamic Properties of Montecellite

A thermochemical study of natural calcium and magnesium orthosilicate monticellite (Ca1.00Mg0.95$${\text{Fe}}_{{0.05}}^{{2 + }}$$)[SiO4] from the Khabarovsk Territory, Russia, was carried out on a Tian–Calvet microcalorimeter. The enthalpy of formation from elements Δf$$H_{{{\text{el}}}}^{^\circ }$$(298.15 K) = –2238.4 ± 4.5 kJ/mol was determined by high-temperature melt solution calorimetry. The enthalpy and Gibbs energy of formation of monticellite of theoretical composition of CaMg[SiO4] are calculated: Δf$$H_{{{\text{el}}}}^{^\circ }$$(298.15 K) = –2248.4 ± 4.5 kJ/mol and Δf$$G_{{{\text{el}}}}^{^\circ }$$(298.15 K) = –2130.5 ± 4.5 kJ/mol.

Natural kaersutite: ftir, raman, thermal and thermochemical investigations

A thermochemical study of the natural oxo-amphibole ─ kaersutite Na0.4K0.3(Ca1.6Na0.4)(Mg2.9Fe0.82+Al0.7Ti0.6Fe0.53+)[Si6.1Al1.9O22](OH)0.2O1.8.(alkaline basalts of Mongolia) was performed on a Tian-Calvet microcalorimeter. The enthalpy of formation from the elements ∆fH el0(298.15 K) = – 12102 ± 16 kJ/mol) was obtained by the method of high-temperature melt solution calorimetry. The entropy, enthalpy and Gibbs energy of the formation of the end-members of the isomorphic series kaersutite NaCa2Mg3TiAl[Si6Al2O22]O2 – ferri-kaersutite NaCa2Mg3TiFe3+[Si6Al2O22]O2 were estimated.

Natural Kaersutite: FTIR, Raman, Thermal, and Thermochemical Studies

The paper reports original thermochemical data obtained on natural oxo-amphibole kaersutite Na0.4K0.3(Ca1.6Na0.4)(Mg2.9 $${\text{Fe}}_{{0.8}}^{{2 + }}$$ Al0.7Ti0.6 $${\text{Fe}}_{{0.5}}^{{3 + }}$$ )[Si6.1Al1.9O22](OH)0.2O1.8 from alkaline basalt in Mongolia. The data were obtained using a Tian–Calvet microcalorimeter. The enthalpy of formation from elements Δf $$H_{{{\text{el}}}}^{{\text{0}}}$$ (298.15 K) = –12102 ± 16 kJ/mol) was obtained by high-temperature melt solution calorimetry. The entropy, enthalpy, and Gibbs energy of formation of the end members of the isomorphic series kaersutite NaCa2Mg3TiAl[Si6Al2O22]O2–ferrikaersutite NaCa2Mg3TiFe3+[Si6Al2O22]O2 were estimated.

Adsorption microcalorimetry as a tool in the characterization of amine-grafted mesoporous silicas for CO2 capture

In this work, amine-grafted mesoporous silica were investigated using a adsorption microcalorimetry and supplementary techniques in order to study the influence of increasing the density of grafted amine on the CO2 binding mechanisms. A Tian–Calvet microcalorimeter coupled to a manometric setup was used to evaluate the energetic heterogeneity of adsorption sites and to calculate the thermokinetic parameter from the differential enthalpy curves. With such device, equilibrium adsorption isotherms of CO2 were simultaneously measured at 25 °C for all samples up to 1 bar. The adsorption microcalorimetric study suggests a change in active sites distribution as the density of grafted amines increases. The maximum thermokinetic parameter of 471 s for the pure silica support at 30.7 kJ mol−1 suggests that physisorption is the dominant binding mechanism. A different behavior occurs with the grafted samples: they have considerably higher enthalpy values corresponding to the formation of reacted species on the surface (chemisorbed CO2), which depend on grafted amine density and available free surface silanols. Kinetics of formation of chemisorption products, together with hindered CO2 diffusion, seriously impair the approach to equilibrium, which leads to a decrease in uptake upon isothermal pressure-swing cycles at low temperatures (25 °C). CO2 could be successfully desorbed at 120 °C from the sample with highest uptake (MSG60), which showed a constant uptake for three adsorption–desorption cycles using only vacuum at 50 °C.

Thermodynamic properties of natural melilites

In the present study, four samples of natural melilites were characterized using electron microprobe analysis, powder X‑ray diffraction, FTIR, and Raman spectroscopy, and their thermodynamic properties were measured with a high-temperature heat-flux Tian-Calvet microcalorimeter. The enthalpies of formation from the elements were determined to be: –3796.3 ± 4.1 kJ/mol for Ca1.8Na0.2(Mg0.7Al0.2Fe20.1+ )Si2O7, –3753.6 ± 5.2 kJ/mol for Ca1.6Na0.4(Mg0.5Al0.4Fe20.1+ )Si2O7, –3736.4 ± 3.7 kJ/mol for Ca1.6Na0.4(Mg0.4Al0.4Fe20.2+ )Si2O7, and –3929.2 ± 3.8 kJ/mol for Ca2(Mg0.4Al0.6)[Si1.4Al0.6O7]. Using the obtained formation enthalpies and estimated entropies, the standard Gibbs free energies of formation of these melilites were calculated. Finally, the enthalpies of the formation of the end-members of the isomorphic åkermanite–gehlenite and åkermanite–alumoåkermanite series were derived. The obtained thermodynamic properties of melilites of different compositions can be used for quantitative modeling of formation conditions of these minerals in related geological and industrial processes.

CO2 gas-adsorption calorimetry applied to the study of chemically activated carbons

In this work, the microporous structure of a series of H3PO4 chemically activated carbons from peach stones with increased activation degree were investigated. CO2 Adsorption equilibrium isotherms and differential enthalpy curves were simultaneously measured at 300K using a Tian-Calvet microcalorimeter coupled to an adsorption manometric setup. Temperature programmed decomposition experiments were used to assess density of oxygen functional groups and determine the impact of surface chemistry on CO2 adsorption capacity. Computer based theoretical calculations were also performed to attempt to predict the adsorption enthalpy profiles. The most activated sample (Xp=0.90) has an average adsorption enthalpy which is approximately 8kJ/mol lower than that of the non-activated samples carbonized under the same conditions. The combination of techniques enabled a better understanding of the pore filling regimes with increasing coverage, since the use of CO2 as a probe gas allows accessing small pores, which otherwise would not be identified from N2 isotherms at 77K. The oxygen content on the carbon surface decreased almost 80% with the increasing degree of activation and did not influence in the CO2 adsorption. Besides providing information about carbon chemistry, CO2 adsorption calorimetry can also be successfully applied to the screening of carbons intended for CO2 capture.

A flow-pulse adsorption-microcalorimetry system for studies of adsorption processes on powder catalysts.

A pulse chemisorption system combining a Tian-Calvet microcalorimeter (Setaram Sensys EVO 600) and an automated chemisorption apparatus (Micromeritics Autochem II 2920) was established to accurately measure differential adsorption heats of gas molecules' chemisorption on solid surfaces in a flow-pulse mode. Owing to high sensitivity and high degree of automation in a wide range of temperatures from -100 to 600 °C, this coupled system can present adsorption heats as a function of adsorption temperature and adsorbate coverage. The functions of this system were demonstrated by successful measurements of CO adsorption heats on Pd surfaces at various temperatures and also at different CO coverages by varying the CO concentration in the pulse dose. Key parameters, including adsorption amounts, integral adsorption heats, and differential adsorption heats of CO adsorption on a Pd/CeO2 catalyst, were acquired. Our adsorption-microcalorimetry system provides a powerful technique for the investigation of adsorption processes on powder catalysts.

CO₂ Capture with Mesoporous Silicas Modified with Amines by Double Functionalization: Assessment of Adsorption/Desorption Cycles.

CO2 adsorption on mesoporous silica modified with amine by double functionalization was studied. Adsorption microcalorimetry was used in order to investigate the influence of increasing the nitrogen surface density on double functionalized materials with respect to the only grafted materials. The distribution of sites and the rate-controlling mechanism of adsorption were evaluated. A Tian Calvet microcalorimeter coupled to a manometric setup was used to evaluate the energy distribution of adsorption sites and to calculate the thermokinetic parameters from the differential enthalpy curves. CO2 and N2 adsorption equilibrium isotherms at 50 and 75 °C were measured with a magnetic suspension balance, allowing for the computation of working capacity and selectivity at two temperatures. With these data, an Adsorbent Performance Indicator (API) was calculated and contrasted with other studied materials under the same conditions. The high values of API and selectivity confirmed that double functionalized mesoporous silica is a promising adsorbent for the post combustion process. The adsorption microcalorimetric study suggests a change in active sites distribution as the amine density increases. Maximum thermokinetic parameter suggests that physisorption on pores is the rate-controlling binding mechanism for the double-functionalized material.

Calorimetric Study of Natural Basic Copper Phosphate—Pseudomalachite

The thermochemical study of a natural basic copper phosphate, pseudomalachite Cu5(PO4)2(OH)4 (Virneberg deposit, Germany), was carried out using high-temperature melt solution calorimetry method with a Tian–Calvet microcalorimeter. The enthalpy of formation of the mineral from elements was obtained to be Δ f Hel(298.15 K) =–3214 ± 13 kJ/mol. The value of the Gibbs energy of pseudomalachite formation calculated using literature data on its standard entropy is Δ f Hel°(298.15 K) =–2812 ± 13 kJ/mol.

Enthalpy of formation of natural hydrous iron phosphate: Vivianite

This paper presents the new data on thermodynamic properties of hydrous iron phosphate, vivianite. The thermochemical study of natural vivianite Fe2.322+Fe0.333+ Mg0.35(PO4)2(OH)0.33·7.67H2O (Kerch iron ore basin, Republic of Crimea, Russia) was carried out on a high-temperature heat-flux Tian-Calvet microcalorimeter “Setaram” (France). The mineral was characterized by X-ray microprobe analysis, powder and single-crystal X-ray diffraction, thermal analysis, FTIR, Raman and Mössbauer spectroscopy. The value of ΔfHm0(T=298.15K) for natural vivianite was found to be −(5217±11kJmol−1). The standard values of the entropy, enthalpy and Gibbs energy of formation at T=298.15K for vivianite of theoretical composition Fe32+(PO4)2·8H2O were calculated as (571.0)J(Kmol)−1, −(5119±19)kJmol−1 and −(4439±19)kJmol−1 respectively.

Thermochemical study of Mg–Fe chlorites

The thermochemical study of two natural trioctahedral Mg–Fe chlorites—clinochlores was carried out using high-temperature melt solution calorimetry with a Tian–Calvet microcalorimeter. The enthalpies of formation of clinochlores of compositions (Mg4.9Fe0.32+Al0.8)[Si3.2Al0.8O10](OH)8 (–8811 ± 12 kJ/mol) and (Mg4.3Fe0.72+Al1.0)[Si3.0Al1.0O10](OH)8 (–8696 ± 13 kJ/mol) from elements were determined. The values of the standard entropies and the Gibbs energies of formation of the studied natural minerals as well as thermodynamic properties of Mg–Fe chlorites of theoretical composition were estimated.